i have a 1999 grand cherokee i have replaced the rad . fan the temp sensor amd fan relay , the fan runs all the time and temp gage is at bottom has code po118 please help

You might need to flush the old coolant and replace with new coolant. http://repairpal.com/obd-ii-code-p0118

at the temp sensor it has 9 volts when I unplug the fan it goes down to 5 volts an the temp gage comes back I have changed the coolant all ready ????

Check all your wiring and connectors, look for shorts, bad grounds or high impedance or other faults.